Various types of displaying devices have been proposed heretofore. In particular, a projector for enlargement projection of a color picture is proposed as a displaying device for a large-sized screen, in which small mirror surface elements are arranged into a plane according to pixels and in which a specular-reflective-type optical modulator, or an image formation element, utilizing reflection of each mirror surface element is used as a picture source.
FIG. 5 is a schematic view showing a structure of a conventional projector. Referring to FIG. 5, the conventional projector is provided with a case 51 in which a light source (luminous source) 52, an image formation element (specular-reflective-type optical modulator) 53 and an imaging optical system 54 are arranged. The imaging optical system 54 includes a refracting optical element such as lens and is attached to one side of the case 51.
When a light 55 emitted from the light source 52 is incident in the image formation element 53, it is modulated according to the image generated by the image formation element 53. The modulated light 55 is enlarged by the imaging optical system 54 and output from the case 51 to be projected on the screen 56 as a projected image.
In the conventional projector shown in FIG. 5, the imaging optical system 54, the image formation element 53 and the light source 52 are fixed in the case 51. Accordingly, the position of the projected image is fixed with respect to the case 51. Therefore, in order to change the position of the projected image on the screen 56, the set up state of the case 51, in other words, the set up posture of the projector itself, needs to be tilted.
An ideal position of the image projected on the screen 56 is determined according to the specification of the projector. In the case where the position of the projected image on the screen 56 is adjusted by tilting the set up position (posture) of the case 51 of the projector, deformation (trapezium distortion) is caused as shown in FIG. 6. In order to acquire projected image without deformation (without trapezium distortion), image signals must be input into the image formation element 53 (i.e., the picture source) according to the length of the shorter side of the trapezium to scale down and modify the length of the longer side of the trapezium, thereby correcting the deformation (trapezium distortion). This requires the operator to manipulate the modification for correction while looking at the projected image.
As described heretofore, according to the conventional projector, the imaging optical system and the like are fixed in the case. Therefore, in order to change the position of the projected image, the set up state of the case itself needs to be changed which is difficult to adjust.
Furthermore, when the case of the conventional projector where it is tilted to adjust the position of the projected image, trapezium distortion of the projected image is caused. In order to acquire a projected image without trapezium distortion, the image signals are input into the image formation element (i.e., the picture source) according to the length of the shorter side of the trapezium to scale down and modify the length of the longer side of the trapezium, thereby correcting the trapezium distortion. This, however, requires the operator to manipulate the modification for correction while looking at the projected image, which is a troublesome work.